tor-browser

aq_complexity.c (6823B)

---

/*
* Copyright (c) 2016, Alliance for Open Media. All rights reserved.
*
* This source code is subject to the terms of the BSD 2 Clause License and
* the Alliance for Open Media Patent License 1.0. If the BSD 2 Clause License
* was not distributed with this source code in the LICENSE file, you can
* obtain it at www.aomedia.org/license/software. If the Alliance for Open
* Media Patent License 1.0 was not distributed with this source code in the
* PATENTS file, you can obtain it at www.aomedia.org/license/patent.
*/

#include <limits.h>
#include <math.h>

#include "av1/encoder/aq_complexity.h"
#include "av1/encoder/aq_variance.h"
#include "av1/encoder/encodeframe.h"
#include "av1/common/seg_common.h"
#include "av1/encoder/segmentation.h"
#include "aom_dsp/aom_dsp_common.h"

#define AQ_C_SEGMENTS 5
#define DEFAULT_AQ2_SEG 3  // Neutral Q segment
#define AQ_C_STRENGTHS 3
static const double aq_c_q_adj_factor[AQ_C_STRENGTHS][AQ_C_SEGMENTS] = {
 { 1.75, 1.25, 1.05, 1.00, 0.90 },
 { 2.00, 1.50, 1.15, 1.00, 0.85 },
 { 2.50, 1.75, 1.25, 1.00, 0.80 }
};
static const double aq_c_transitions[AQ_C_STRENGTHS][AQ_C_SEGMENTS] = {
 { 0.15, 0.30, 0.55, 2.00, 100.0 },
 { 0.20, 0.40, 0.65, 2.00, 100.0 },
 { 0.25, 0.50, 0.75, 2.00, 100.0 }
};
static const double aq_c_var_thresholds[AQ_C_STRENGTHS][AQ_C_SEGMENTS] = {
 { -4.0, -3.0, -2.0, 100.00, 100.0 },
 { -3.5, -2.5, -1.5, 100.00, 100.0 },
 { -3.0, -2.0, -1.0, 100.00, 100.0 }
};

static int get_aq_c_strength(int q_index, aom_bit_depth_t bit_depth) {
 // Approximate base quatizer (truncated to int)
 const int base_quant = av1_ac_quant_QTX(q_index, 0, bit_depth) / 4;
 return (base_quant > 10) + (base_quant > 25);
}

static bool is_frame_aq_enabled(const AV1_COMP *const cpi) {
 const AV1_COMMON *const cm = &cpi->common;
 const RefreshFrameInfo *const refresh_frame = &cpi->refresh_frame;

 return frame_is_intra_only(cm) || cm->features.error_resilient_mode ||
        refresh_frame->alt_ref_frame ||
        (refresh_frame->golden_frame && !cpi->rc.is_src_frame_alt_ref);
}

// Segmentation only makes sense if the target bits per SB is above a threshold.
// Below this the overheads will usually outweigh any benefit.
static bool is_sb_aq_enabled(const AV1_COMP *const cpi) {
 return cpi->rc.sb64_target_rate >= 256;
}

void av1_setup_in_frame_q_adj(AV1_COMP *cpi) {
 AV1_COMMON *const cm = &cpi->common;
 const int base_qindex = cm->quant_params.base_qindex;
 struct segmentation *const seg = &cm->seg;
 const int resolution_change =
     cm->prev_frame && (cm->width != cm->prev_frame->width ||
                        cm->height != cm->prev_frame->height);

 // Make SURE use of floating point in this function is safe.

 if (resolution_change) {
   memset(cpi->enc_seg.map, 0, cm->mi_params.mi_rows * cm->mi_params.mi_cols);
   av1_clearall_segfeatures(seg);
   av1_disable_segmentation(seg);
   return;
 }

 if (is_frame_aq_enabled(cpi)) {
   int segment;
   const int aq_strength =
       get_aq_c_strength(base_qindex, cm->seq_params->bit_depth);

   // Clear down the segment map.
   memset(cpi->enc_seg.map, DEFAULT_AQ2_SEG,
          cm->mi_params.mi_rows * cm->mi_params.mi_cols);

   av1_clearall_segfeatures(seg);

   if (!is_sb_aq_enabled(cpi)) {
     av1_disable_segmentation(seg);
     return;
   }

   av1_enable_segmentation(seg);

   // Default segment "Q" feature is disabled so it defaults to the baseline Q.
   av1_disable_segfeature(seg, DEFAULT_AQ2_SEG, SEG_LVL_ALT_Q);

   // Use some of the segments for in frame Q adjustment.
   for (segment = 0; segment < AQ_C_SEGMENTS; ++segment) {
     int qindex_delta;

     if (segment == DEFAULT_AQ2_SEG) continue;

     qindex_delta = av1_compute_qdelta_by_rate(
         cpi, cm->current_frame.frame_type, base_qindex,
         aq_c_q_adj_factor[aq_strength][segment]);

     // For AQ complexity mode, we dont allow Q0 in a segment if the base
     // Q is not 0. Q0 (lossless) implies 4x4 only and in AQ mode 2 a segment
     // Q delta is sometimes applied without going back around the rd loop.
     // This could lead to an illegal combination of partition size and q.
     if ((base_qindex != 0) && ((base_qindex + qindex_delta) == 0)) {
       qindex_delta = -base_qindex + 1;
     }
     if ((base_qindex + qindex_delta) > 0) {
       av1_enable_segfeature(seg, segment, SEG_LVL_ALT_Q);
       av1_set_segdata(seg, segment, SEG_LVL_ALT_Q, qindex_delta);
     }
   }
 }
}

#define DEFAULT_LV_THRESH 10.0
#define MIN_DEFAULT_LV_THRESH 8.0
// Select a segment for the current block.
// The choice of segment for a block depends on the ratio of the projected
// bits for the block vs a target average and its spatial complexity.
void av1_caq_select_segment(const AV1_COMP *cpi, MACROBLOCK *mb, BLOCK_SIZE bs,
                           int mi_row, int mi_col, int projected_rate) {
 if ((!is_frame_aq_enabled(cpi)) || (!is_sb_aq_enabled(cpi))) return;
 const AV1_COMMON *const cm = &cpi->common;
 const int num_planes = av1_num_planes(cm);

 const int mi_offset = mi_row * cm->mi_params.mi_cols + mi_col;
 const int xmis = AOMMIN(cm->mi_params.mi_cols - mi_col, mi_size_wide[bs]);
 const int ymis = AOMMIN(cm->mi_params.mi_rows - mi_row, mi_size_high[bs]);
 int i;
 unsigned char segment;

 // Rate depends on fraction of a SB64 in frame (xmis * ymis / bw * bh).
 // It is converted to bits << AV1_PROB_COST_SHIFT units.
 const int64_t num = (int64_t)(cpi->rc.sb64_target_rate * xmis * ymis)
                     << AV1_PROB_COST_SHIFT;
 const int denom = cm->seq_params->mib_size * cm->seq_params->mib_size;
 const int target_rate = (int)(num / denom);
 double logvar;
 double low_var_thresh;
 const int aq_strength = get_aq_c_strength(cm->quant_params.base_qindex,
                                           cm->seq_params->bit_depth);

 low_var_thresh =
     (is_stat_consumption_stage_twopass(cpi))
         ? AOMMAX(exp(cpi->twopass_frame.mb_av_energy), MIN_DEFAULT_LV_THRESH)
         : DEFAULT_LV_THRESH;

 av1_setup_src_planes(mb, cpi->source, mi_row, mi_col, num_planes, bs);
 logvar = av1_log_block_var(cpi, mb, bs);

 segment = AQ_C_SEGMENTS - 1;  // Just in case no break out below.
 for (i = 0; i < AQ_C_SEGMENTS; ++i) {
   // Test rate against a threshold value and variance against a threshold.
   // Increasing segment number (higher variance and complexity) = higher Q.
   if ((projected_rate < target_rate * aq_c_transitions[aq_strength][i]) &&
       (logvar < (low_var_thresh + aq_c_var_thresholds[aq_strength][i]))) {
     segment = i;
     break;
   }
 }

 // Fill in the entires in the segment map corresponding to this SB64.
 const int mi_stride = cm->mi_params.mi_cols;
 set_segment_id(cpi->enc_seg.map, mi_offset, xmis, ymis, mi_stride, segment);
}